The present invention relates to a digital copier having an image reader (scanner) and an image writer (plotter) which are physically independent of each other, and, more particularly, to a digital copier having a single image reader and a plurality of image writers which are cooperatively associated with each other.
A digital copier having a single image reader and two or more image writers which are implemented as a scanner and plotters, respectively, has been proposed. With this type of digital copier, one may designate any of the image writers to cause it to perform writing operations, i.e. copying operations. Assume a jam or similar error has occurred in an image writer having been designated and performing writing or copying operations. Then, it has been customary to interrupt the writing or copying operations and, after the removal of the error such as the removal of a jamming sheet, to resume the copying operations by using the same image writer.
In the prior art digital copier operable with a particular image writer as designated by the operator, when the designated image writer is already performing copying operations, a command on a start key or similar copy input key is not accepted and a document cannot be inserted in an automatic document feeder (ADF). Since no further copying operations can be reserved at the image writer in operation, one cannot press the copy input key or insert a document in an ADF without awaiting the end of copying operations of the image writer of interest. Another drawback with the prior art copier of the type described is that interrupting the operations to remove a jamming paper, for example, and then resuming the operation by using the same writing unit adds to the copying time due to the need for an extra error settling time. Especially, the error settling time is critical when it comes to errors of the kind which cannot be removed without a service manual.